The finding refers to the anterior forks for bicycles or motorcycles, in particular to the telescopic forks for the so-called mountain bikes or off road bicycles, or for off-road motorcycles, which are typically used on bumpy terrain and/or steep uphill or downhill slopes. The finding specifically refers to these telescopic forks equipped with upper cross braces or star cross with a seat in the center into which the end of the steering column is connected. And is equipped at the ends with seats into which the ends of the parallel pipes are connected and opposite to the steering pipe and are meant to slide telescopically in solid sheaths with the bottom end at the wheel hub, which are in every telescopic equipment as supplied with elastic methods which normally maintain the same unit in an extended position, with shock absorbing systems being foreseen.
For the connection of said pipes to the star cross, different methods are currently being used which are however, difficult to automate, are not quickly carried out, and are not at a good level of technological reliability. To resolve the noted technical problems in the specific aforesaid area, the finding proposes a method which includes:
a phase in which the pieces to be reciprocally connected are manufactured, with tolerances such that the external diameter of the ends of the pipes is properly greater to the internal diameter of the star cross end seats;
a heating phase for the star cross, at a temperature which does not promote permanent deformities in the piece and is sufficient to slightly increase the internal diameter of the pipe mounting seat;
a cooling phase at the proper temperature of the ends of the pipes, preferably through the immersion of said extremities into liquid nitrogen, in a manner such that the external diameter of the pipes themselves shrinks in a suitable manner;
rapid and easier insertion of the cooled and contracted pipe ends, in the seats of the dilated end of the heated star cross, without having the disadvantage of a pressure connection occur, since the ends of the pipes enter into the seats of the star cross without or with a slight interference. When the star cross and the pipes return to room temperature, they turn out to be fixed and connected with the expected tightness.
The apparatus for carrying out of said method includes:
a loading station for the pipes and the star cross pieces, all of which are upside down with respect to the position they are used in, having been set in a vertical preset position, while the others are placed horizontally;
at least one robot arm, equipped at the end with a pair of pliers for the outside, to grasp the a couple of pipes and equipped with at least one plier for the inside, to grasp the star cross for the central seat which is intended to carry the steering pipe;
a possible station to check the internal diameter of the star cross seats and the external diameter of the ends of the pipes, immediately after the pieces have been taken from the loading station;
an oven in which said robot arm cyclically inserts a star cross taken from said loading supply and extracts a heated one,
a station with a tank to stock liquid nitrogen and is open on top in order to permit the introduction of the ends of the pipes,
an assembly station, equipped with the means to hold an overturned star cross horizontally, taken from the oven and the means to support above the seat ends of this, of the corresponding overturned and cooled pipes on their lower ends and equipped with the means to properly center the pipes and to push the same with their lower ends into said seat ends of the star cross;
a station for collecting and removing the star crosses with the pipes mounted.